AB0796 Quantitative bone marrow lesion characterization at the sacroiliac joint with T1-mapping
Authors: T. Diekhoff, D. Deppe, D. Poddubnyy, K. Ziegeler, F. Proft, K. G. Hermann, M. Protopopov, F. Radny, M. Makowski
Journal: Annals of the Rheumatic Diseases (2022)

Background Conventional magnetic resonance imaging (MRI) uses T1-weighted and short-tau inversion recovery (STIR) sequences to characterize bone marrow lesions in axial spondyloarthritis. However, quantification is restricted to the extent of marrow lesions because signal intensities are highly variable within and across patients and scanners. Furthermore, some marrow lesions are less visible in MRI and need further characterization with computed tomography (CT), e.g. sclerosis. Quantitative MRI in form of mapping sequences might help to better characterize bone marrow lesions. Objectives To evaluate the performance of T1-mapping for differentiating different bone marrow lesions at the sacroiliac joints in patients with suspected axial spondyloarthritis. Methods Sixty-two patients (mean age 41±12.5; thirty-two were finally diagnosed with axial spondyloarthritis and 30 with another condition) underwent CT and MRI of the sacroiliac joints. Besides standard oblique coronal T1 and STIR sequences a T1-mapping sequence (Modified Look-Locker Inversion Recovery) was added to the protocol. Bone marrow lesions (maximum 4 lesions per patient, 1 lesion of the same type per joint) were characterized by an expert radiologist into four groups, namely sclerosis (lesion type (LT) 1), osteitis (LT2), fat lesion (LT3) and mixed marrow lesions (LTm). Relaxation times on T1-maps were compared using Kruskal-Wallis test correcting for multiple comparisons and correlated to quantitative measures from conventional MRI sequences and CT. Results 119 lesions were selected (LT1: 38, LT2: 27, LT3: 40; LTm: 14). T1-map showed highly significant differences between LT1-3 with the lowest values for sclerosis (1522±227 ms), followed by osteitis (1906±82 ms) and fat lesions (2391±200 ms); p&lt;0.0005. However, mixed lesions showed a broad distribution of values (1869±670), irrespective of their characteristics. T1-map correlated to a high degree with conventional T1-values (r = 0.74) and Hounsfield units in CT (r = -0.69) with p &lt; 0.0001, respectively, but not with STIR (p = 0.8). Conclusion T1-Mapping allows for accurately characterizing lesions at the sacroiliac joint in patients with suspected axial spondyloarthritis and, thus, may combine information from two conventional sequences and CT into one in the future while providing superior capacity for quantification. However, in our study mixed lesions and inhomogeneous bone marrow remained problematic. Thus, further sequence development is needed before its implementation in clinical routine. Figure 1. T1-mapping values of the different lesions, LT1: Sclerosis, LT2: Osteitis, LT3: Fat lesion, LTm: Mixed lesion. Differences are highly significant, which allows T1-mapping to characterize those different lesions in one sequence. Disclosure of Interests Torsten Diekhoff Speakers bureau: Novartis, Eli Lilly, MSD, Canon MS, Consultant of: Novartis, Dominik Deppe: None declared, Denis Poddubnyy: None declared, Katharina Ziegeler: None declared, Fabian Proft: None declared, Kay-Geert Hermann: None declared, Mikhail Protopopov: None declared, Felix Radny: None declared, Marcus Makowski: None declared